Method of applying a chemical conversion coating solution to a metal surface



June 29, 1965 N. J. NEWHARD, JR 3,

METHOD OF APPLYING A CHEMICAL CONVERSION COATING SOLUTION TO A METAL SURFACE Filed Sept. 4, 1962 EICJ-i INVENTOR w g. may

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United States Patent 3 192,974 h/iEilHfiD @F APPLYlhJG A @HEMZCAL (IQNVER- tiifBN QQA'HNG SQLUEEGN T0 A METAL SUR- FACE Nelson J. Nev/hard, 3n, Greland, Pan, assignor to Amchem Products, inc, Ambler, Pa, :1 corportion of Deiaware Filed Sept. 4, 1962, Ser. No. 221,111 tilaizns. (til. 148 614) This invention relates to the art of applying conversion coatings to metal surfaces and is more particularly concerned with the application of such coatings to the surfaces of sheet-like pieces or to elongated, relatively thin strips of the metal and involves themethod of applying the conversion coating solution to the surfaces undergoing treatment. I

By way of background it should be pointed out that it is frequently necessary to produce extremely uniform conversion coatings over large surface areas and also that it is often desirable toapply a coating of greater weight on one side of a metal strip or sheet than on the A good example is a sheet where one side is to be painted but not the other. On the side where paint is to be applied only a relatively light weight conversion coating may be needed while for the other side a heavier coating may be indicated in order to promote adequate corrosion resistance. Furthermore, it is often necessary to produce such coatings on extremely thin and fragile sheets or strips of metal, particularly aluminum for special purposes, without tearing or in any way damaging the sheet.

With the foregoing problems in mind one of the principalobjects of the present invention is to provide a method and an apparatus for the conversion coating of large surface areas of relatively thin sheets or strips of metal, particularly aluminum, whereby extremely uniform coatings can be produced on the surface without tearing or damaging the metal or in any way impairing its integrity and strength.

It is also an object of the invention to apply chemical conversion coatings in the manner indicated on both sides of a sheet or strip simultaneously and at the same time to make the coating on one side heavier than on the other where so desired.

A still further object is to apply conversion coatings to metal surfaces, especially to large areas,.in such a way as to yield substantially complete uniformity throughout the entire coated area as to appearance, emiscivity, rellectivity, dielectric resistance, etc.

How the foregoing objectives are attained will now be described in connection with the accompanying drawing, wherein FIGURE 1 is a diagrammatic side view of an apparatus for carrying out the method of my invention, and

FIGURE 2 is a diagrammatic end view of the apparatus shown in FIGURE 1.

In the drawing there is shown a tank 3 substantially filled with a chemical conversion coating solution 4 to provide a bath in which to effect the coating treatment.

An elongated strip of very thin metal 5, such as aluminum,

enters the bath from the left and passes out on the right as indicated by the arrows, the strip being suitably guided as by rollers 6, 7, 8 and h and being moved through the bath in any desired manner, not shown. The strip passes over the rollers 6 and 9 and under the rollers 7 and 8, which latter are located well down in the bath so as to provide, preferably, a horizontal run or length of strip which at all times is completely submerged in the i 3,.lii2fiiid Fatented June 29, 1965 ice openings or spray heads 11 which discharge downwardly against the upper face of the strip as shown by the lines 12. A similar series of manifold pipes 16a having openings or spray heads'lla are arranged below the strip to discharge upwardly against the under face of the strip as shown by the lines 12a. The manifold pipes it are fed by a supply pipe 16b and the pipes 19a by a supply pipe 160, there being a regulating control valve 10d in the, pipe ltib and a similar regulating control valve ltie in the pipe 10c. The two supply pipes are in communication with the interior of the tank 3 through a circulation pipe 13 which draws solution from a point near the bottom of the tank under the influence of a pump 14.

In the event that the tank is large in relation to the width of the metal strip under treatment it may be found to be desirable to insert a bafile 15 in a relatively close proximity and parallel to each side of the strip which baffles act as a confining means to concentrate or contain the flow of the discharged solution over the region of the strip surface under treatment.

Obviously, the number and arrangement of the flow inducing outlets or sprays may be varied, the degree of opening of the regulating valves may be adjusted, and the speed of the pump may be altered to meet the requirements of any particular situation.

It will be clear from all of the foregoing that the quantity of solution that is caused to flow over either surface of the strip may be altered as desired. When more coating solution is forced to flow over the surface a heavier coating will be produced and when less solution is flowed over the surface a lighter coating results. My invention, therefore, makes-it possible to regulate within reasonably accurate limits the amount or weight of coating that will be applied to the surface and also that less coating can be applied to one side than to the other and that this can be done simultaneously in the same bath.

The invention is of particular value in the coating of extremely thin sheets or strips of aluminum because the buoying effect of the solution on the submerged sheet or strip minimizes the possibility of the thin metal being torn or damaged by the force of the sprayed solution. Where the strip is not submerged spray applications of the solution constitute a real hazard to maintaining the integrity of the thin metal.

I' claim:

1. In the art of applying a chemical conversion coatig solution to the surface of metal; the method which comprises submerging a spraying means in a bath of the conversion coating solution, submerging the metal in the bath adjacent said submerged spraying means, and spraying solution through saidspraying means against the surface of the metal while it is submerged.

2. In the art of applying a chemical conversion coating solution to the opposite surfaces of an elongated, thin metal strip; the method which comprises submerging opposed spraying means in a bath of the conversion coating solution, submerging the strip in and moving it through the bath between said opposed spraying means, and spraying solution through said spraying means simultaneously against both surfaces of the strip as it passes through the bath,

3. The method of claim 2 wherein more solution is sprayed against one surface of the strip than against the other. 7 r

4. In the art of applying a chemical conversion coating solution to a thin metal sheet; the method which comprises submerging opposed spraying means .in a bath ing solution through said spraying means simultaneously against both surfaces of the sheet.

5. The method of claim 4 wherein more solution is 2,310,451 sprayed against one surface than against the other. 2,381,183 2,458,525 References Iited by the Examiner 2 77 143 UNITED STATES PATENTS 5 2,890,944

1,579,003 3/26 Koch 118 -419 2,141,382 12/38 Perm 118429 X 2,254,216 9/41 Gordon.

Marshali 148--6.15

Richards 1486.15 Nachtman 2. 117-64 X Drysdale 148-6.15 Hays 1486.15 X

RICHARD D. NEVIUS, Primary Examiner.

WILLIAM D. MARTIN, Examiner, 

1. IN THE ART OF APPLYING A CHEMICAL CONVERSION COATING SOLUTION TO THE SURFACE OF METAL; THE METHOD WHICH COMPRISES SUBMERGING A SPRAYING MEANS IN A BATH OF THE CONVERSION COATING SOLUTION, SUBMERGING THE METAL IN THE BATH ADJACENT SAID SUBMERGED SPRAYING MEANS, AND SPRAYING SOLUTION THROUGH SAID SPRAYING MEANS AGAINST THE SURFACE OF THE METAL WHILE IT IS SUBMERGED. 